Biodiversity is the variation in living organisms, viewed within a given habitat, ecosystem or in the world as a whole. The concept is usually applied to the species diversity, although the notion of genetic biodiversity is applied to the variation in genes within an individual species. While most people think of rainforests as loci of great biodiversity, biomes such as oceans and grasslands are the likely repositories for even greater variation. Retention of diverse biota is important, since intact ecosystems are thought to be essential for provision of ecosystem services to humans, including maintenance of a diverse foodbank, pollination, clean water, flood control, pest control, waste decomposition, biomass energy resources and climate stability. Biodiversity is presently critical since we live in the era of the Mass Holocene Extinction, a period of species loss caused by man, and unrivaled in rate of species loss. Although the number of total species numbers in the tens of millions, most have not yet even been described. The extinction of a species is almost always related to destruction of habitat or man-made pollution.
The Permian period lasted from 290 to 248 million years ago and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the...
Species richnessLast Updated on 2014-11-09 19:13:40Species richness is simply the number of species present in a sample, community, or taxonomic group. Species richness is one component of the concept of species diversity, which also incorporates evenness, that is, the relative abundance of species. Species diversity is one component of the broader concept of biodiversity. About 1.75 million living species and 300,000 fossil species have been described by scientists. Estimates of the total species richness of the Earth range from three to 10 million, with some estimates as high as 50 million.
Patterns of species richness can be observed at a variety of levels. The causes of these patterns remain active areas of research in ecology, biogeography, and evolutionary biology.
Some taxonomic groups of organisms have more species than other groups. For example, there are almost three times more species of beetles (Order Coleoptera) than... More »
Species range limitsLast Updated on 2014-11-09 18:49:44Species range limits (SRLs) are defined as the spatial boundaries beyond which no living individuals of a given species occur. Populations occurring near or at SRLs are often referred to as “marginal,” “peripheral,” “edge,” or “border” populations. SRLs may represent areas beyond which individuals cannot physiologically tolerate ecological conditions or areas where they have not yet dispersed. SRLs may be stable (i.e., at equilibrium) or may represent areas where range expansion through migration or population growth is in the process of occurring. SRLs are significant to ecology, evolution, and conservation for several reasons. They provide opportunities to understand the conditions under which populations expand or contract, and the conditions under which populations may evolve new forms. Additionally, SRLs... More »
Umbrella speciesLast Updated on 2014-11-09 18:40:24
The concept of an umbrella species has been used by conservation practitioners to provide protection for other species using the same habitat as the umbrella species. As the term implies, a species casts an “umbrella” over the other species by being more or equally sensitive to habitat changes. Thus monitoring this one species and managing for its continued success results in the maintenance of high quality habitat for the other species in the area. Animals identified as umbrella species typically have large home ranges that cover multiple habitat types. Therefore, protecting the umbrella species effectively protects many habitat types and the many species that depend on those habitats. Although the effectiveness of this conservation approach is debated, it is often used by practitioners to select a minimum size for protected... More »
DeforestationLast Updated on 2014-11-09 17:48:51Deforestation is the destruction or clearing of forested lands, usually for the purposes of expanding agricultural land or for timber harvesting. When the process is conducted by clearcutting (removal of most or all of the canopy tree growth, leaving few or no live or dead trees standing) or when mass forest burning occurs, significant losses of habitat and biodiversity may result, including the erosion of biological community structure and the extinction of species. Deforestation is proceeding at a rapid pace in may areas of the world, especially in the tropical and boreal forest regions of the earth, with annual net loss of forests during the 1990s estimated in the range of nine to sixteen million hectares per annum. Large scale deforestation may have adverse impacts on biosequestration of atmospheric carbon dioxide, exacerbating greenhouse gas buildup, through the release of stored... More »
Biological diversity in the HimalayasLast Updated on 2014-11-04 11:46:06
Stretching in an arc over 3,000 kilometers of northern Pakistan, Nepal, Bhutan and the northwestern and northeastern states of India, the Himalaya hotspot includes all of the world's mountain peaks higher than 8,000 meters. This includes the world's highest mountain, Sagarmatha (Mt. Everest) as well as several of the world's deepest river gorges.
This immense mountain range, which covers nearly 750,000 km2, has been divided into two regions: the Eastern Himalaya, which covers parts of Nepal, Bhutan, the northeast Indian states of West Bengal, Sikkim, Assam, and Arunachal Pradesh, southeast Tibet (China), and northern Myanmar; and the Western Himalaya, covering the Kumaon-Garhwal, northwest Kashmir, and northern Pakistan. While these divisions are largely artificial, the deep defile carved by the antecedent Kali Gandaki River between the Annapurna and Dhaulagiri... More »
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